The fire spread meter predicts the average potential rate of forward spread of the head fire over periods of 15-20 minutes.

The short-term variation around this average value is quite high; users may find rates of spread in the field varying by 25 per cent of the predicted value if they make observations over periods of less than 10 minutes.

At high wind speeds, the potential rate of spread of a fire is not achieved until the width of the head fire is greater than 200 metres. The meter will therefore over-predict rates of spread in the first 15-20 minutes of a fire's development, or if the head fire remains narrow for any reason.

For wildfires burning under low to moderate wind speeds, the predicted potential rate of spread may also be greater than the observed rate. This is because, under these conditions, fires may be held up for brief periods by such things as roads, green gullies or firebreaks, so that the average rate of spread determined by timing a fire's movement past features in the landscape may be substantially lower than the spread across continuous pasture.

In addition, the scale of the meter is not appropriate for determining rates of spread at zero wind speed, and for practical purposes it is better to use a minimum wind speed of five km/h when winds are light and variable during the day.